1. Field of the Invention
Methods consistent with the present invention relate to data writing and reading of a memory device, and more particularly, to data writing and reading of a memory device employing magnetic domain wall movement.
2. Description of the Related Art
Due to developments in information technology leading to a requirement for high capacity data storage, demand for data storage media capable of storing large quantities of data continues to increase. Accordingly, data storage speed has been augmented, methods of compacting storage devices have been developed, and as a result, a wide variety of data storage devices has been developed. A widely-used data storage medium is a hard disk drive (HDD), which includes a read/write head, and a rotating medium on which data is recorded, and has the capacity for recording 100 gigabytes (GB) of data or more. However, the rotating parts in storage devices such as HDDs have a tendency to wear, so that the reliability of such devices is compromised by the likelihood of a failure during operation after a prolonged period of use.
Research and development is currently underway on a new data storage device that uses a magnetic domain wall movement principle.
FIGS. 1A through 1C illustrate a principle of moving a magnetic domain wall. In FIG. 1A, a magnetic wire includes a first magnetic domain 11, a second magnetic domain 12, and a magnetic domain wall 13 between the first and second magnetic domains 11 and 12.
A magnetic micro region within a magnetic material will hereinafter be referred to as a magnetic domain. In the magnetic domain, the rotation of electrons, that is, the direction of the magnetic moment of the electrons is the same. The size and magnetization direction of such a magnetic domain can be adjusted by altering the type of magnetic material, its shape, and size, as well as applied external energy. A magnetic domain wall is a partition with magnetic domains having respectively a variety of different magnetized magnetization directions. The magnetic domain walls may be moved through the application of a magnetic field, a current applied to a magnetic material or through a current.
As illustrated in FIG. 1A, after a plurality of magnetic domains disposed in predetermined directions are created in a magnetic layer with a predetermined width and thickness, the magnetic domains may be moved using magnetic fields or currents.
Referring to FIG. 1B, when a magnetic field is applied in a direction from the second magnetic domain 12 to the first magnetic domain 11, the magnetic domain wall 13 may move in the same direction as the direction from the second magnetic domain 12 to the first magnetic domain 11, that is, in the same direction of the application of the external magnetic field. Using the same principle, when a magnetic field is applied in a direction from the first magnetic domain 11 to the second magnetic domain 12, the magnetic domain wall 13 moves in a direction from the first magnetic domain 11 to the second magnetic domain 12.
Referring to FIG. 1C, when an external current is supplied in the direction from the first magnetic domain 11 to the second magnetic domain 12, the magnetic domain wall 13 moves in a direction from the second magnetic domain 12 to first magnetic domain 11. When a current is supplied, electrons flow in the opposite direction to the direction of the current, and the magnetic domain wall 13 moves in the same direction as the electrons. The magnetic domain wall moves in the direction opposite to that of the externally supplied current. When a current is supplied in the direction of the first magnetic domain wall 11 from the second magnetic wall 12, using the same principle, the magnetic domain wall 13 moves in a direction from the first domain 11 to the second domain 12.
In summary, a magnetic domain wall can be moved using an applied external magnetic field or current.
The principle of moving magnetic domains may be applied to a memory device such as an HDD or a read only memory (ROM). Specifically, an operation for reading/writing binary data of ‘0’ and ‘1’ is possible by using the principle of changing the magnetic arrangement within a magnetic material by moving a magnetic domain wall of the magnetic material having magnetic domains magnetized in predetermined directions and magnetic domain walls representing the boundaries there between. A specific current is passed through a linear magnetic material to change the positions of the magnetic domain walls to read and write data. Thus, a highly integrated device with a simple structure may be used. Therefore, compared to conventional memories, such as ferroelectric random access memory (FRAM), magneto-resistive random access memory (MRAM), and phase-change random access memory (PRAM) devices, the principle of moving a magnetic domain wall can be applied to memory devices with much larger storage capacities. However, applying the moving of magnetic domain walls to semiconductor devices is still in the initial stages of development, and has a comparatively low data storage density. Therefore, there is a need for memory devices employing magnetic domain wall movement with structures optimized for high-density devices.